In 2020, a viral video of an unusual interaction between a badger and a coyote captivated the internet. Filmed by a camera with a remote sensor in California’s Santa Cruz Mountains, the images showed the two animals into a culvert to pass under a highway. With a wagging tail, the coyote ran toward the badger and then away again, pausing to see if the badger would follow. The badger hurried to catch up with his companion, and they trotted into the tunnel together.
Their playful behavior suggested that the pair had a friendly bond. But can animals really be friends, like humans are?
In many social animal species, certain behaviors suggest that individuals may indeed be closer to some than to others (beyond close relatives or mates). Male dolphins that forage on sponges hang out with other males that a similar foraging styleElephants use specific greetings to other elephants they know. Primates show intimate bonds with non-relatives by to polishRooks are also known to groom certain rooks in their flock, they polish with their beaks.
“Individuals form social relationships to make sense of their environment,” he said. Delphine De Moora postdoctoral researcher in behavioral biology at the University of Exeter in the United Kingdom. For highly social animals, relationships are defined by varying levels of trust and intimacy, De Moor told Live Science. Patterns of interaction form these bonds; trust grows when repeated interactions are positive.
If animals can form bonds that are stable, long-lasting and mutually beneficial – qualities that are also found in human friendships – “then we do indeed see friendship in the animal kingdom,” De Moor said.
Scientists studying primates have discovered that neurochemistry plays a major role in strengthening such bonds, Catherine Crockfordresearch director at the French National Centre for Scientific Research (CNRS) in Lyon and head of The Great Ape Social Mind Lab.
In primates, grooming releases the behavior-regulating hormone oxytocin, “which then goes into the reward center, presumably providing a positive feedback system so you’re more likely to groom yourself again,” Crockford told Live Science. Grooming a friend also reduces cortisol, a hormone associated with stress. In contrast, cortisol levels are unaffected when monkeys groom a group member they’re not bonded with, Crockford added.
“It seems like there are some physiological benefits to, say, caring for your partner who you have a bond with,” she said.
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Scientists first reported reciprocal friendships among primates through observations of matrilineal monkey groups, but in recent decades, mounting evidence has emerged about friendship and its benefits in other mammals, Crockford said.
“Individuals who are able to maintain these strong relationships end up living longer, having more offspring, and showing fewer signs of related stress,” she said. “It really seems like if you can maintain these kinds of relationships, they have very profound benefits.”
For example orcas share food and information about where to find foodOrcas that have strong bonds within their pod are less likely to starve when resources are scarce. Hyenas with more friends tend to be more successful within their clans because they have support in social challenges.
But with friendship comes responsibility, De Moor added. “At a certain point,” she said, “animals are willing to take much more risks, much more costly behaviors for their preferred social partners.”
Think of the self-sacrifice of a vampire bat who helps a hungry friend by sharing recently swallowed meals and throw up blood in a friend’s mouth (and if you haven’t thrown up in your friend’s mouth lately, can you even call yourself a friend?).
Among chimpanzees, friendship bonds can be so strong that if a mother dies and leaves behind a dependent young, “a male or female friend [of the parent] could adopt that offspring,” Crockford said. Raising a youngster comes at a cost to the new parent, especially if the adopter is male, she added.
“His general pace of life has to slow down,” Crockford said. “He’s going to have to carry the offspring or go at their pace, and share his nest with them at night, and can’t get involved in group interactions or aggressive interactions with others as quickly.”
Interspecies friendship
Mutual trust can also occur between species. In 2022, a groundbreaking study showed that wild chimpanzees and gorillas in the Republic of Congo can cross the species barrier and form friendships that last 20 years or more.
In some cases, friendships between animals are forged through human intervention. Cats and dogs that share a home often develop close bonds. In a private zoo in Belgium, a family of Orangutans Befriended a Roaming Otterafter the caretakers merged their habitats. A lion and a dog In Mexico, the two, who had grown up together (the lion was kept illegally as a pet), remained close after they were both transferred to an animal shelter.
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While the display of playful camaraderie between the badger and the coyote in California has never been observed before, such interspecies relationships may be more common in the wild than scientists suspect, De Moor said. Much more is known about friendships between animals in some groups — primates, elephants and dolphins, for example — simply because their social behavior has been observed for decades, with some relationships studied throughout the animals’ lives.
“We only know what we study, and we don’t know what we don’t study,” De Moor said.
Evidence of friendship among animals in general (and primates in particular) sheds light on the evolution that shaped humans’ capacity for friendship, Crockford noted. Our last shared ancestor with apes lived about 25 million years agoSo the neurochemistry behind human friendship and associated behaviors has existed for millions of years.
“These mechanisms are deep and ancient,” she said. “In this day and age, when there are other things that people may value more than friendships — like money or fame or clicks — it’s a really nice reminder that a fundamental part of us is designed to have friends. And that if we can have friends and we’re serious about our friends, we’re going to live longer and be healthier and less stressed.”